The present invention relates generally to an improved water-based vinyl latex base coat resin coating formulation together with a top coat formulation which is adapted for use therewith. More particularly, the present invention relates to a water-based vinyl resin containing film former which may be applied to a variety of surfaces, particularly foam resin articles, through a variety of application techniques or systems, with the film forming formulations being capable of forming a thick durable base coat with highly desirable adherent and coherent properties along with a top coat which improves overall durability of the composite coating. The uncured base coat material is reasonably viscous and highly adherent to surfaces upon which it is applied, properties which it retains while in the liquid state. Once the base coat material has been applied and permitted to cure, the residual thick coating or film possesses sufficiently high cohesive strength so as to render the dried film extremely tough and durable, and with sufficiently high adhesive strength so as to render the coating resistant to peel or other premature failure or release. When the base-coat material has been permitted to dry or otherwise cure through reaction and solvent (water) removal, a durable, pliable, flexible, and yet tough coating is created. This material cures uniformly and the coating is created without premature surface curing or skinning which would otherwise impede the loss of excess solvent from an uncured core. The top coat component, when applied to the base coat, provides a more glossy surface coating, and also adds to the durability of the coated article by adhering or otherwise bonding firmly to the base coat so as to provide it with added slip and toughness, as well as improving the water resistance. The top coat formulation, when added to the base coat, has also proven to enhance the weatherability of the overall coating as well as that of the coated article.
In addition to the improved properties of the coating, the formulations of the present invention have been found to reduce the emissions of volatile organic compounds (VOC) by amounts ranging from between 50% and 90%. This reduction in emission of VOC is achieved without sacrificing the appearance and/or quality of products coated with the improved formulations. Indeed, the appearance and quality of products coated with the formulations of the present invention are equal in most respects to those with solvent-based formulations.
The coating material of the present invention has been found highly adaptable for application to flexible articles, particularly articles fabricated from plastic, including plastic in foam form. Of particular interest are foam articles utilized in the sports industry, including floatation devices as well as body protection devices fabricated from foam and utilized as foam mats for wrestling and/or gymnastics, as well as foam knee pads and foam elbow pads.
It is recognized that the requirements of the state, local and federal EPA authorities, as well as compliance with OSHA regulations has increased interest in industry with water-base coatings. More restrictive conditions are being placed upon discharge of solvent vapors into the atmosphere, inasmuch as certain, but not all, solvents have been found to be health risks. When dealing with the coating of foam articles, solvent-base coatings tend to form anomalies in the foam article, including deformation of the foam structure and accordingly deformation of the substrate. While water-based systems have been recognized as representing a solution to the emissions and substrate deformation problems, water-based coating systems have generally not achieved the properties available from most solvent-based systems. The formulations of the base coat and top coat composites of the present invention, while water-based, create base coats and top coat composites which possess many of the properties previously only available in solvent-based systems.
The formulations of the present invention producing the composite coating has been found to reduce the frictional characteristics between the surface of the article and the athlete's body. Because of the improved durability and improved water resistance, the articles are easily cleaned with water or mild detergents and/or solvents.
Application techniques for the base coat, while in liquid form, are wide and varied, and may include dipping, brush application, or spray application. Relatively thick base coatings may be prepared from a single dipping operation, and viscosity control may accommodate the preparation of coatings of from as thin as about 2 mils but preferably greater, such as from about 8 mils up to about 12 to 15 mils. Base coats having such a thickness may be created using an operation as simple as a single dipping of the article into a supply of the formulation.
In the preparation of conventional coating formulations, particularly base coat formulations, it is generally desired that the film forming layer, particularly when in cured form, have appropriately designed and matched adhesive and cohesive properties. The physical and mechanical properties of the substrate may also be a factor in the design of the adhesive and cohesive properties of the base coat. Normally, these properties are tailored so that the bond which is formed by the adhesive material preferably fails due to simultaneous failure of both its adhesive and its cohesive properties. At the same time, it is generally desirable that the film possess a relatively high peel strength and that this property not be sacrificed in the pursuit of appropriate adhesive and cohesive strength. The formulations of the present invention are designed to possess high adhesive and cohesive strength so as to provide for coating and/or film durability along with appropriately high peel strength. Additional features of the formulations of the present invention include the characteristic of preparing reliable coatings through dipping of foam plastic articles, thereby facilitating the coating of these otherwise difficult-to-coat articles with a durable, pliable, flexible and tough film.
The desirable physical properties, particularly the adhesive quality of the formulations of the base coat of the present invention appear to make dip-coating operations possible. By way of example, the consistency of the liquid base coat material permits application in either single or multiple dip operations, with a thick and durable film being prepared. While films having such properties are particularly desirable for the coating of plastic foam articles, the formulations of the present invention are also useful as film formers for coating other articles as well, including rigid metallic articles and the like. Films and coatings formed in accordance with the present invention retain their good physical properties, including flexibility and durability, over extended periods of time and even while subjected to low temperatures.
The dual and composite coatings of the present invention have wide application to form coatings for objects fabricated from polyvinylchloride, vinyl/nitrile, polyethylene, including polyethylene foam in lineal, radiated cross-linked and/or chemically cross-linked form, polypropylene, polypropylene foam, polyurethane foam, expanded polystyrene (styrofoam), and the like.